1. Field of the Invention
The present invention relates to a method and apparatus for partitioning a block for motion compensation in inter prediction in which a block is effectively partitioned using a cost of a ½ block.
2. Discussion of Related Art
H.264/MPEG-4 AVC is a video compression standard which was jointly developed in 2003 by the ITU-T Video Coding Experts Group (VCEG) and the ISO/IEC Moving Picture Experts Group (MPEG). H.264 is 1.5 to 2 times higher in compression rate than MPEG-2 or MPEG-4 but requires a large amount of encoding process. A ratio of the amount of inter prediction process to the whole encoding process is increased due to functions such as variable block size, a maximum of five reference frames, and ¼ pixel motion compensation, which were adopted to increase encoding efficiency.
Many studies have been conducted to effectively perform encoding process, but a study on high speed processing of a function which is newly added to H.264 has not sufficiently been conducted. A technique for effectively selecting a search block size using pixel value differences between a target macroblock to be encoded and a macroblock of a reference frame has been suggested. However, when this technique is applied to searching a plurality of reference frames, a search block size differs among the reference frames, and it is less likely to partition a block into two blocks either vertically or horizontally when selecting a search block size, so that the encoding rate deteriorates.
FIG. 1 shows block partitions used in H.264 inter prediction scheme.
Referring to FIG. 1, in H.264 inter prediction scheme, a total of 7 block sizes of from 16×16 to 4×4 can be used. Since various block sizes can be used, prediction can be performed by flexibly changing a block size with respect to portions that are quite different from a reference frame and portions that are similar to the reference frame, so that difference values between frames can be reduced. Also, although the computation amount may be increased by referring many frames, the amount of encoded data is reduced, so that compression efficiency is more improved.
However, since determination of a block partition size in a frame requires a long process time and a large amount of process, there is a need for a method for effectively partitioning a block.